Go to your map and follow the side quest, turn off the waypoints for both Main quests. follow it dead on and you'll eventually find a camp with a fire. Eat from it 5 or 6 times and make sure you're stuffed by eating a piece of food from your inventory, got to sleep in a nearby tent. Rinse and repeat. Sometimes you'll have to use wait instead, as you can only sleep a certain amount of hours a day.